This invention relates to a fuel supply regulating apparatus and, more particularly, to a fuel supply regulating apparatus for regulating the fuel supply to an engine in accordance with the fuel mixture ratio of the fuel such as the methanol concentration in gasoline.
FIG. 5 illustrates, in a schematic diagram, the main portion of a conventional fuel property detecting apparatus disclosed in Japanese Patent Laid-Open No. 58-129235, for example. In FIG. 5, a transparent prism 1 of a triangular cross-section has jointed thereon a similar but hollow triangular prism 2 through which fuel 3 flows. These transparent prisms 1 and 2 are held together by a housing 4 which has on its opposite sides openings 4a.
Adjacent to the housing 4, a light source 5 is disposed to face to one of the openings 4a of the housing 4 through a slit plate 6 which shapes the light from the light source 5 into a light beam 7.
On a light path of an outcoming light beam 7a from the second opening 4a, a light amount detection plate 8 is provided. The light amount detection plate 8 has formed therein a longitudinal slit 9 having a gradually changing width. A collective lens 10 is disposed for collecting and focusing the light beam passing through the slit 9 onto a light sensor 11 which senses the amount of light that impinges on the light sensor 11. The light sensor 11 has connected thereto a controller 12 for controlling the fuel supply to an engine (not shown), such as by controlling the period of time during which the fuel injection valve (not shown) is opened or the degree of opening of the fuel pressure regulator (not shown).
The operation will now be described. The light beam 7 emitted from the light source 5 passes through the slit plate 6 and into the hollow transparent prism 2, from where the light beam 7 travels from the fuel 3, the hollow prism 2 and through the solid prism 1 while being refracted at each interface, and is emitted from the housing 4 through the second opening 4a to impinge upon the light amount detection plate 8.
The light 7a reached to the light amount detection plate 8 only partially passes through the slit 9 because of the limited width of the slit 9, and is collected by the collecting lens 10 to be focused on the light amount sensor 11.
The refraction factor at an interface A between the fuel 3 and the hollow transparent body 2 varies in accordance with the characteristics of the fuel, i.e., the ratio of mixture of the different kinds of fuels within the fuel 3. Therefore, when the mixture ratio changes, the refraction angle at the interface A varies and the position at which the light beam 7a impinges at the light amount detection plate 8 varies accordingly in the longitudinal direction (up and down directions in the figure). On the other hand, since the slit 9 of the light amount detection plate 8 is longitudinally tapered, the light amount detected by the light amount sensor 11 varies in accordance with the ratio of mixture of the different fuels in the fuel 3.
As the light amount sensor 11 detects the light, a signal according to the light amount is provided to the control unit 12, and thus the control unit 12 controls the valve opening time of the fuel injection valve and the fuel pressure regulator in accordance with the signal.
The above operation will now be described in more detail using an example in which a different fuel of methanol is mixed into gasoline.
When the fuel 3 contains only gasoline which has a refraction factor of about 1.51 which is relatively small, the position at which the light beam 7a impinges at the light amount detection plate 8 is on the upper portion of the plate as viewed in the figure, so that the light amount that can pass through the slit 9 is decreased.
On the other hand, when methanol which has a refraction factor of about 1.33 is mixed with gasoline which has a refraction factor of about 1.51, the resultant refraction factor of the mixed fuel is a value between 1.33 and 1.51 which varies according to the mixed ratio. That is, as the ratio of amount of methanol within the fuel increases, the refraction factor of the fuel 3 decreases, so that the refraction angle becomes small and the position at which the light beam 7a impinges upon the light amount detection plate 8 moves to a lower position as viewed in the figure. Thus, the light amount that passes through the slit 9 increases as the mixture ratio of methanol increases.
Thus, since the light amount that is received by the light amount sensor 11 varies in accordance with the mixture ratio of methanol in gasoline, the fuel character can be determined by measuring the light amount.
Other types of the conventional design is also known in which the position at which the light beam 7a impinges can be directly detected by a semiconductor element, a diode array, an image sensor or the like to determine the fuel characteristics.
In the conventional fuel supply regulating apparatus as above described, the refraction factor of the fuel 3 is measured by the signal from the light amount sensor 11, and a separate control unit 12 for controlling a fuel pressure regulator, a fuel injection valve actuator or the like on the basis of the above measured results is necessary, so that the system is disadvantageously expensive.